Terminal bushing with thin paper insulation



L. P. MACARDIER TERMINAL BUSHING WITH THIN PAPER INSULATION 2 SHEETS-SHEET l Aug. 12, 1952 Filed Dec. 2, 1946 '//Il/l/I A IN V EN TOR.

ATTORNEYS Aug. 12, 1952 l.. P. MACARDIER 2,606,950

TERMINAL BUSHING WITH THIN PAPER INSULATION Filed Dec. 2, 194e 2 SHEETS-SHEET 2 W .if I M .5 235 y 5 INVENToR. L .P Macaffdz'ef ATYUHNEYS Patented Aug. 12, 1952 TERMINAL BUSHIN G WITH rIHIN PAPER INSULATION Louis Pierre Macardier, Lyon, France, assignor to Compagnie Generale dElcctricite, Paris, France, a corporation of France Applieauuu December 2, 1946, serial Nu. 713,435 In France June 1, 1944 section 1, Public Law 69o, August s, 1946 Patent expires June 1, 1964 12 Claims.

In apparatus such as the bushing terminals of electric apparatus, the bushing terminals of high voltage transformers, and the end boxes of cables, the voltage is distributed either radially or longitudinally by means of metal parts or intersheaths embedded between the different layers of the insulation. These devices are made by winding around the conductor insulating bands with interposed metal layers as of foil. 4

Hitherto there have been used for this purpose insulating bands of considerable width wound by machine on themselves, with the metal layers or intersheaths interposed. Since these condensers so formed have most often the general form of a double cone, the insulating bands to be wound khave a decreasing width, but always equal to the'total height of the insulation in each concentric cylinder around the central conductor. Thus in these prior art constructions, the insulating bands have a very considerable width in the neighbourhood of the ycentral conductor, this width remaining always fairly large in the intermediate layers of the condenser.

This method of manufacture, as heretofore emp'loyed, in spite of its apparent simplicity, has serious disadvantages; it vdoes not permit of avoiding the formation between the different layers of the wound insulation of air pockets producing either irregularities inthe surface of the paper, or of the width of the'bands, preventing at places their correct arrangement on the neighbouring layers. v

Moreover, in these prior art constructions, due to the presence'of these metal intersheaths or electrodes, the insulation forms a body which is`not very permeable to thev impregnating oils or materials. It happens in these arrangements heretofore used, that the temperature variations of the cable in use cause empty spaces to be formed in the insulating mass of the sleeve, which considerably reduce the dielectric strength of the whole. K

The present invention avoids these disadvantages. A iirst object of the present invention consists in forming each layer of the insulation, or at least the central layers of such a condenser, which will often be of impregnated paper, by winding in a cylindricalspiral a narrow insulating band; this winding is preferably provided with abutting spirals or turns.

Another object of the present invention consists in impregnating the paper bands of the insulation before winding with a relatively light uid oil of the kind used for high-tension cables with oil circulation, and impregnating the whole assembly body after the winding operation with a uid oil of the same kind.

Another object of the present inventionrelates particularly to the case wherein the insulation has such a large thickness that in spite of the improved method of impregnation the variations of the temperature during use may produce empty spaces in certain parts of this thickness. In order to prevent such a possibility the present invention provides a continuous permanent impregnation of the insulation, after the winding, under a certain pressure, by making it communicate with the oil under pressure when the installation is put into service and during its operation.

.It will be appreciated that between the various phases of the impregnating operations, especially after the winding of the insulation bands, it is advantageous to proceed in a known manner to a vacuum treatment of the insulation in order to expel air and humidity by heating.

In the end sleeves for cables which themselves are continuously subjected to ay pressure of fluid oil, the permanent impregnation of the sleeves and the cable can be effected bybne or more of the special containers provided for supplying voil to the cable. f

Fig. 1 shows in cross section the winding insulating layer structure of a cable terminal according to the present invention.

Fig. 2 shows a wound terminal structure mounted in a treatment sleeve for the application of heat and vacuum and subsequent oil impregnation. y

Fig. 3 shows a wound terminal structure mounted in the usual operating outer porcelain shell, for a final vacuum and oil impregnation treatment, without heat.

Fig. 4 shows the use of a varnished silk envelope to separate a cable terminal into two separate spaces to permit the use of oils of two different qualities for cables insulated by paper impregnated with viscous material.

Fig.v 5 shows a cable terminal assembly constructionhaving a communicating channel between the interior of the terminal and the oil circulation of the cable itself, to permit use of a common oil supply for both cable and terminal. y Fig. 6shows a cable terminal construction divided into separate low pressure outer and high pressure inner concentric compartments .separated by an insulating tube, for use withcables operating under' high oil pressure.

Figure 1 shows diagrammatically the construc- Ation of a winding of the terminal insulation used by the present invention. -In .this drawing, the

.accesso 'central electric conductor is indicated by I and the diierent insulating layers by 2. Each of them is composed of a cylindrical spiral the different successive turns of which are indicated by 2', 2". 2n. It is to be noted that, due to this staggered method of winding, there are obtained between the diilerent layers, high reluctance leakage paths, an advantage additional to those indicated above.

The metal layers or intersheaths of the winding structure are indicated by 3. Each layer of which a metal layer or intersheath forms a part is continued to the ends of the condenser winding structure by an insulating band 4 of the same thickness, in such manner as to obtain a single cylindrical surface permitting a satisfacy moisture, andthen to introduce into this porcelain envelope fluid oil in order to impregnate the insulation of the condenser, these two operations being effected at the ambient temperature.

According to the present invention, this treatment of the wound insulation is considerablyimproved by heating the insulation, at least-while it is under. vacuum, and preferably also during impregnation. In order to carry out this operation, the present invention provides the use of a special 'heating sleeve which is Vremoved at the end of these operations, to be replaced by the normal insulating porcelain shell envelope of the completed terminal, within which the two operations of drying and impregation are repeated.

Figures 2 and 3 of the drawings showing in sec` tion respectively an embodiment of one-end of the cable during the heat treatment, and in its nished assembly, will permit of a better understanding of this feature of the present invention.

As indicated in Figure 2, the condenser terminal structure 5 mounted on the end of the cable is surrounded by a metal treatment sleeve 6 connected by sealed coupling 1 to a metal cap 8 which has been soldered at 9 tothe lead of the cable. This cap B serves for the nal mounting of the end of the cable.

The treatment sleeve 6 is provided with a nozzle I0 connected to a vacuum pump and comprises a resistance heating device I2. At the respective ends of the sleeves 6 there are provided two nozzles II and I3 and, according to the position of the cable end, one of these nozzles permits of removing the oil in the course of the drying operation, the other of introducing the oil forrelling.

In order to dry the insulation, the inside of the treatment sleeve 6 is heated by the resistance I2 to about 120 C. and a vacuum is produced inside the sleeve by the nozzle I9, the oil being drawn through the nozzle II orv I3.

For the purpose of raising the temperature of the condenser structure for drying purposes, the sleeve 6 may be lled with oil before the vacuum is applied, vand heated, and when a temperature of 110 to 120 C. is obtained in the mass of the 4 wound insulation the oil is withdrawn and the vacuum applied.

The condenser 5 having been thus dried, is impregnated by closing one of the nozzles II or I3 and lling the sleeve 6 with oil through the other, the vacuum being maintained during the filling operation.

When the end of the cable is thoroughly impregnated, its final mounting in the hanged porcelain insulating shell I4, represented by Figure 3, is eifected, and it is then subjected to a .new vacuum operation, without heat, and to impregnation with oil. For this purpose, the metal tip of the usual anged porcelain insulating shell has a nozzle I0' connected to the pump and the impregnating oil flows, as in the first operation, through the nozzle I3.

As shown in Figure 3, the two halves of the envelope of the condenser terminal structure are locked together in tight manner and fixed with their ends registering with an orifice in an adaptor plate I5. To eiect this assembly, there is employed a metal sleeve I6, one end of which is soldered to the cap 8 after removal of the heating sleeve 6. The other end of the sleeve IS is secured by means of bolts I1 and ange I8 against the porcelain outer shell Inl, with an interposed joint I9, and fixed on the plate I5.

Figure 4 shows an end sleeve assembly for a cable insulated by paper which is impregnated with a viscous material. The cable 2l whose conductor 22 is covered with the normal wrapped insulation 23 of the cable, impregnated as above explained, is covered with a lead sheath or en-y velope 24, which extends slightly into the end sleeve. In the interior of this sleeve the wrapped insulating part 23, stripped of its lead cover, is surrounded Vby an insulating envelope 25 imper- `rneable to the impregnating materials and also covering in a tight manner the junction between the uncovered part of the insulation 23 and its lead sheath cover 24. This envelope 25 consists of one or several layers of insulating impermeable windings, such as varnished silk.

The insulation structure 26 arranged around the impermeable partition envelope `25is that to which the invention relates, and it consists of wound paper bands impregnated with the relatively light fluid oil of the kind used in high- .tension cables with oil circulation and interposition of metal intersheaths or electrodes 21. The cable terminal formed in this manner is placed in the interior of a tight sleeve Vformed by a `cap 28and an outer porcelain shell insulator 29 and provided with a supplying pipe 39 leading to an appropriate oil supply source. n

After assembly of the parts, there follows the described treatment with vacuum'and heating, then the sleeve 28, 29 is lled with fluid oil of the kind used for the preceding impregnation of the paper bands, forming the wound insulation structure 26, before winding. This Viilling may be effected by a container 3| similar to those used forrlling cables having oil circulation. When the impregnation is finished, the container can be removed, or can remain connected to the sleeve inthe regular service of the installation, in order to subject the insulation of the sleeve to a permanent impregnation. In both cases, the presence of the impermeable insulating envelope 25 prevents the mixing of the two oils of different quality which impregnate respectively the insulation 26 of the sleeve 28, 29 and that of the vcable itself, which latter is viscous.

.In systems using cables with Vlight uid oil circulation, the oil container for supplyingfthe nd sleeve may be the same as that for the cable itself. It is then suiiicient to establish a. communication betweenk the interior of the terminal sleeve and the oil circulation conduits of the cable. This communication, shown in Figure may be eiected by a channel 32 traversing the binding screw 33 in case of a cable with a central channel, or by the lead tube 34 in case of a cable with peripheral channels, or in both ways in case ofva cable having both types of' channels.

In the case of cables with fluid oil circulation operating under high pressure and comprising end sleeves covered with an insulator shell; for instance of porcelain, not strong enough for these pressures, each terminal sleeve is subdivided into two concentric tight compartments, the peripheral compartment being lled with an insulating oil subjected to a pressure lower than that impregnating the wound insulation 26 of the cable end which is located in the central compartment. This embodiment is shown in Figure 6 in which the separating wall between the two compartments consists of an insulating tube 35.

The oil impregnating in a permanent manner the wound insulation 26 of the cable end sleeve in the interior of this separating tube 35, is the same oil under high pressure as that impregnating the cable from the container 3| owing to the existence of the communication channels 32 lor 34 already described in thel preceding embodi-l ments. The permanent filling ofthe outer peripheral compartment with an oil of a lower pressure is secured by a separate container 36.

In installations ycomprising cables under .veryy high tension, operating underV very high voil pressures, which also permit the permanent lilling of the cable terminal sleeves with impregnating oil it is possible to appreciably reduce the thickness of the wound insulation condenser structure by using as the paper bands constituting that structure paper bands made of ilax paste, which are rst impregnated with oil of the kind impregnating the cable itself, and have an individual thickness between 0.01 and 0.04mm.;

to prevent breaking down of the winding it is i suflicient to use bands of small width. The use of thin paper of low permeability is made possible by the high pressure of the oilwhich allows the maintaining of an impregnation suilicient to avoid any empty space in the insulating condenser structure in spite of the temperature variations of the cable end during operation.

The preceding dispositions which have just been described for end boxes of cables can be used also for bushing terminals of transformers and other electric apparatus.

It will be apparent to those skilled in the art that my invention is susceptible of modifications to meet particular applications, and all such modifications which are within the scope of the appendedclaims, I consider to be comprehended within the spirit of my invention.

I claim:

1. In high tension electrical equipment, a high tension electric cable including a conductor havlng insulation thereon, a fluid-tight insulating casing spacedly surrounding a portion of said insulated conductor and in sealed relation to said insulation thereon, wound paper band condenserstructure insulation closely surrounding said insulation on that portion of said conductor Within said casing and including a plurality of layers of narrow paper bands having a thickness up to 0.04 mm. wound in closely adjacent spirals about the axis of said conductor and thin metal sheaths alternating with at least some of the 4layers of insulating paper, said condenser-structure insulation being impregnated with relatively light Huid cable oil, and a reservoir for said relatively light iluid cable oil and permanently connected with said casing for continuously supplying said iluid oil to said casing and to said paper band insulation within said casing for permanent impregnation of said last-mentioned insulation.

2. In high tension electrical equipment, a high tension electric cable including a conductor having insulation thereon, a fluid-tight insulating casing spacedly surrounding a portion of said insulated conductor and in sealed relation to said insulation thereon, Wound paper band condenserstructure insulation closely surrounding said insulation on that portion of said conductor Within said casing and including a plurality of layersof narrow paper bands having a thickness up to 0.04 mm. Wound in closely adjacent spirals about the axis of said conductor and thinmetal sheaths alternating with at least some of the layersof insulating paper, f said condenser-structure insulation being impregnated with relatively light uid cable oil, and a reservoir `for said relatively light fluid cable oil and permanently connected with said casing for continuously supplying said iiuid oil under super-atmospheric pressure to said casing andto said paper band insulation within said casing for permanent impregnation of said last-mentioned insulation, n

3. In high tension electrical equipment, a high tension electric cable including a conductor having insulation thereon, a fluid-tight insulating casing spacedly surrounding a portion of said in sulated conductor and in sealed relation to said insulation thereon, wound paper band co-ndenserstructure insulation closely surrounding all of the insulated portion of said conductor within said casing and including la plurality of layers of narrow paper bands having a thickness upto 0.04 mm. wound in closely adjacent spirals about the axis of said conductor and thin metal sheaths alternating with at least some of the layers of insulating paper, said condenser-structure insulation being impregnated with relatively light iluid cable oil, and a reservoir for said relatively light fluid cable oil and permanently connected with said casing for continuously supplying said uid oil under super-atmospheric pressure to said casing and to said paper band insulation within said casing for permanent impregnation of said lastrnentioned insulation.

4. In high tension electrical equipment, a sheathed cable including a conductor having high tension insulation thereon, a conductor extending from said cable beyond the sheath thereof asa continuation of the conductor of said cable and having insulation thereon constituting a continuation of at least that part of the insulation Within said cable which is immediately adjacent the conductor in said cable, a iluid-tightv insulating casing spacedly surrounding said insulated conductor extension and sealed to the sheath of said cable, Wound paper band condenser-structure insulation closely surrounding said insulation on that portion oi said conductor within said clasing and including a plurality of layers of narrow paper bands having a thickness up to 0.04 mm. Wound 'in closely adjacent spirals about the axis of said conductor and thin metal sheaths, alterhating with at least some of the layers of insulating paper, said condenser-structure insulation being impregnated with relatively light iiuid cable oil, and a reservoir for said relatively light fluid cable'o-il andconnected with said casing and to `said' paper bandinsulation within said .casing for permanent impregnation .of said last-mentioned insulation.

5. In high tension .electrical equipment, a high tension electric cable including .a conductor having insulation thereon, a fluid-tight insulating casing in sealed relation to said insulation on said conductor and spacedly surrounding a portionof said conductor Vhaving insulationthereon which isa continuation of at least that portion of said inst-mentioned insulation which is adjacent to said conductor, wound paper band condenser-structure insulation closely surrounding said insulation on that portion of said conductor within said casing and including a plurality of layers of narrow paper bands having a thickness up to 0.04 inm. Wound in closely adjacent spirals aboutthe axis of said conductor and thin metal sheaths alternating with at le-ast some of the layersof insulating paper, said condenser-structure insulation being impregnated with relatively light fiuid-cable oil, and a reservoir `for'said relatively light iiuid cable oil and .permanently connected with said casing for continuously supplying said nuid oil under super-atmospheric pressure to'said casing'and to said paper band insulation within said casing for permanent impregnation of` said last-mentioned insulation.

6. In high tension electrical equipment, acable including a conductor having insulation thereon, a conductor extending from said cable as :a continuation of the conductor thereof and having insulation thereon as a continuation vof at least that part of the insulation of saidcable which is immediately adjacent the conductor of said cable, a fluid-tight insulating casing spacedly surrounding said insulated conductor extension and Vin sealed relation'to said cable, Wound paper band condenser-structure insulation closely surrounding said insulation on that portion of saidconductor` within said casing and including a plurality of layers of narrow paper bands having a thickness up to 0.04 mm. Wound in Yclosely adjacent spirals about the axis of said conductor and thin metal sheaths alternating with at least some of v the layers of insulating paper, said .wound paper band insulation being impregnated with relatively light fluid cable oil, and the periphery of said Wound paper vband insulation expanding to impart a convex profile thereto vfrom vthe end thereof yadjacent said cable and then decreasing toward the opposite end thereof,`and a reservo-ir for said relatively light fluid cable oil permanently connected With said casing for continuously supplying said duid oil to said casing and to said paper band insulation within said casing for permanent impregnation of said last-mentioned insulation.

'7. In high tension electrical equipment, a sheathed cable including a conductor having thereon insulation impregnated with relatively heavy viscous oil, a conducto-r extending from said cable as a continuation'of the conductor of said cable and having insulation thereon as a continuation of at least that part of the insulation Within said cable Which is immediately adjacent the conductor in said cable, a fluid-tight insulating casing spacedly surrounding said insulated conducto-r extension and sealed to the sheath of said cable, an oil-impermeable insulating wall encircling said insulation on said conductor `extension and dividing said casing into coaxial chambers, Wound paper band condenser-structure insulation in the outermost of said chambers 'and closely surrounding'said Wall and vsaid insulation on that portion of .said conductor within said casing Aand including a plurality of rlayers of narrow paper bands .having a thickness upto 0.04 mm. Wound in .closely adj acent `spirals about the axis of said conductor and thin metal sheaths alternating with layers of kinsulating paper, said- Wound paper band Yinsulation being impregnated with relatively light vfluid cable oil, anda reservoir for said relatively light fluid cable oil permanently connected to said outer chamber for permanent impregnation ofsaid condenser-structure insulation. 1

8. In high tension electrical equipment.` a cable including a conductor having oil-impregnated Wrapped insulationfthereon, a fluid-tight insulating casing spacedly surrounding a portion of ysaid insulation and in Vsealed relation to said-cable. Wound paper band condenser-structure insulation closely surrounding `alliof said insulation on that portion of said conductor Within said-casing and including a plurality of layers of narrow paper bands having a thickness up to 0.04 Wound in closely adjacent spirals about the axis of said conductor -andthin metal sheaths alternating lwith layers of insulating paper, 'said Wound paper bandinsulationbeing impregnated with uid cable oil, and a reservoir for said fluid cable oil permanently connectedwith said'casing for continuously maintaining a supply of said fluid o-il under super-atmospheric pressure to said casing and to saidA paper band insulation and wrapped insulation within said casing.

9. In high tensionelectrical equipment, a cable including an electric conductor having insulation thereon, a fluid-tight insulatingcasing spacedly surrounding a' portion Aof'said insulated conductor and in sealed relation to said cable, Jan oil-im'- permeable insulating Wall extending longitud? nally of said casing and surrounding saidlinsulated conductor with said "casing and dividing said casing into two coaxial chambers, Wound paper band condenser-structure' insulation .disposed within a' iir'st'on'e of said chambers and coaxial with that portion of saidconductor withinsaid casing and including a'plurality 'of Ilayers of narrow paper bands havinga thickness ,upto 0.04 mm. Wound Iin closely adjacent spirals 'about the axis of saidconductor and thin metalsheaths alternating With Ylayers of insulating paper, said wound paper band insulation 4*being impregnated with relativelylight yfluid circulating cable oil, a reservoir of said iiuidcable oil permanently connected with the last-mentioned chamber for ccntinuously maintaining I:a supplyof said relatively light fluid oil to saidfirstchamber and to said paper band insulationwithin said casingior continuously applying said light uid oil for permanent impregnation 'of said condenser-structure insulation therewith, and insulating oil disposed within the other' of said chambers. I

10. In high tension electrical equipment, Va. cable including a conductor having insulation thereon and having a fluid oil circulation passage containing light nuid circulating oil,v a` conductor extending from said cable as a continuation of the conductor 'of said cable and .having insulation thereon ras a continuation o f at least that part oi ,the :insulation withn'saidvcable which is immediate-ly :adj acent the f conductor insa-id cable, a fluid-tight insulating casing spacediysurrounding said insu-latedconductor extension and sealed to the sheathof said cable, the interior .of said casing being-incommunication with saidoil pasjsage o'f the cable, wound paper band vcondenserstructure insulation closely surrounding said insulation on that portion of said conductor within said casing and including a plurality of layers of narrow paper bands having a thickness up to 0.04 mm. wound in closely adjacent spiralsy about the axis of said conductor and thin metal sheaths alternating with layers of insulating paper, said wound paper band insulation being impregnated with relatively light iluid cable oil, and a reservoir for said relatively light fluid cable oil permanently connected with said casing for continuously applying said fluid oil for permanent impregnation of said condenser-structure insulation therewith.

11. In high tension electrical equipment, a sheathed cable including a conductor having insulation thereon, said cable containing oil under high pressure and having an oil circulation passage therein, a conductor extending from said cable as a continuation of the conducto-r of said cable and having insulation thereon as a continuation of at least that part of the insulation within said cable which is immediately adjacent the conductor in said cable, a uuid-tight insulating casing spacedly surrounding said insulated conductor extension and sealed to the sheath of said cable, an oil-impermeable insulating wall extending longitudinally of said casing and spacedly surrounding said insulated conductor within said casing and dividing said casing into two coaxial chambers one within the other, the interior of the innermost of said chambers being in communication with the high-pressure oil passages of the cable, wound paper band condenserstructure insulation in said inner chamber and closely surrounding said insulation on that portion of said conductor within said chamber and including a plurality of layers of narrow paper bands having a thickness up to 0.04 mm. wound in closely adjacent spirals about the axis of said said high-pressure oil permanently connected with said inner chamber for continuously applying said oil under high pressure for permanent impregnation of said condenser-structure insula- 10 Y tion therewith, and a source of supply of oil under relatively lower pressure connected to the outermost of said chambers.

12. In high tension electrical equipment, an insulated conductor, a fluid-tight insulating casing spacedly surrounding a portion of said insulated conductor, an oil impermeable insulating tube extending longitudinally of said casing and sur rounding said insulated conductor and dividing said casing into two coaxial chambers, wound paper band condenser-structure insulation positioned in a first one of said chambers and closely surrounding said insulated conductor, said wound paper condenser-structure insulation including a plurality of layers of narrow paper bands wound in closely adjacent spirals and having a thickness up to 0.04 mm. and thin metal shields alternating with at least some of said layers of paper, said wound paper band insulation being impregnated with relatively light fluid circulating cable oil, a reservoir of the said relatively light fluid circulating cable oil connected to said iirst chamber of said casing containing said oil for permanent impregnation of said paper band insulation therewith, and an insulating oil positioned in the second one of said chambers.

LOUIS PIERRE MACARDIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,691,356 Morrison Nov. 13, 1928 1,759,419 Rump May 20, 1930 1,878,016 Steinmeyer Sep-t. 20, 1932 2,209,894 Scott et al July 30, 1940 2,255,832 Thompson Sept. 16, 1941 2,276,923 Burr Mar. 17, 1942 2,287,201 Scott June 23, 1942 2,298,211 Guzik Oct. 6, 1942 2,309,992 Scott Feb. 2, 1943 FOREIGN PATENTS Number Country Date 439,575 England Dec. 9, 1935 

